As it turned out, Santa's stone allowed him to prevent magic, use magic, or redirect magic. Basically, it gave him control over any magic being used in his presence. But how would that help in the current situation? Yes, he tried to make use of it to manipulate the wish that Karyn had made, but for some reason, he wasn't able to. Was something preventing him? Or was his stone broken? He hoped not, because right now, he could really use some help.
Where was Santa right now, anyway?
